00:01
So we have a normal distribution, and we're supposed to have the mean amount of time that the commercial takes is 75 seconds, and the standard deviation is 20 seconds, quite a bit of variability.
00:14
And we want to find in part a, what is the likelihood that a commercial lasts less than 35 seconds? and if we go like so, if we go down here is one standard deviation below, so that would be 55.
00:27
We go down two standard deviations below, and that's going to be 35.
00:31
So this is going to correspond without even doing any work as far as converting to a z value.
00:36
I can see that it's going to be at a score of negative 2, a z value of negative 2.
00:42
And the area below negative 2 is 0 .028.
00:47
Then in part b, we want to find the likelihood that a commercial will last longer than 55 seconds.
00:55
And i can see from this that that means we want the z value to be bigger than negative 1...